Active temperature feedback control of continuous casting

ABSTRACT

The invention includes a system, method and machine readable program for dynamically controlling the casting of a material. Generally, the systems and methods described herein include an active control feedback system or aspects thereof including a temperature sensing device that is well-suited for the harsh environment of the interior of a caster such as a caster for casting metal. Temperature measurement can be accomplished either directly or indirectly. The system is configured to compare the measured temperature with an ideal casting temperature. The temperature sensing device is operably coupled to a cooling device that modulates a flow of coolant to dynamically cool the material being cast. In accordance with one embodiment of the invention, the cooling device includes a plurality of nozzles for delivering one or more cooling fluids to the material being cast.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority of U.S. ProvisionalApplication Ser. No. 60/796,074 filed Apr. 28, 2006. This application isrelated to U.S. patent application Ser. No. 11/709,070 filed Feb. 21,2007. Each of these applications is incorporated by reference herein inits entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to continuous casting machines andparticularly to the control of the secondary cooling in the continuouscasting machines where molten metal is molded into cast slabs, strands,billets and the like.

2. Description of Related Art

In a continuous casting machine (or “caster”) as depicted in FIG. 1,molten metal 1 is poured into a cooled copper faced mold 2 whichcontrols the physical width and thickness of the finished product. Metalexits the mold 2 in the form of a strand or slab having a thin shell 3of solidified metal with a core 4 of molten metal. The strand continuesinto a secondary cooling zone 5 to further solidify the metal. As themetal passes through the machine it is gradually cooled (secondarycooling) with water sprays or water/air mix sprays 6 which are used toconvert the molten metal from a liquid state to a semi-solid state as itchanges direction from the vertical into the horizontal direction forhandling and processing. The rate of cooling has a direct effect on themetallurgical characteristic of the metal being produced and there is anideal cooling curve, known to those skilled in the art, that should befollowed in order to achieve best product.

Unfortunately because of the design of modern continuous castingmachines, limited control of temperature is possible. From the exit fromthe mold to the horizontal point, the continuous casting machine lengthis divided into zones and preset water flow values are available toincrease or decrease the volume of cooling water to those zones in orderto achieve an exit temperature from the zone. Currently, the metalsurface temperature is measured with optical pyrometers or similardevices. However, no successful attempts have been made to integratethat temperature to a predetermined curve such as an ideal curve, andimprecise cooling is the result.

It is desirable to keep the surface temperature of the metal controlledin a manner to prevent surface cracks or internal defects, which mayoccur if the metal is cooled too quickly, or prevent a breakout ofmolten metal from the core of the slab. Breakout is a major problem.Breakout occurs when the thin shell of the strand of material breaks,allowing the still-molten metal inside the strand to spill out and foulthe casting system, requiring an expensive shutdown. Often, breakout isdue to too high a withdrawal rate, as the shell has not had the time tosolidify to the required thickness, or the metal is too hot, which meansthat final solidification takes place below the straightening rolls andthe strand breaks due to stresses applied during straightening. Atypical breakout can cost a steel mill $250,000 and it is not uncommonto have two or three breakouts per month.

Either of these failures results in costly further processing, waste, orexpensive and dangerous consequences to personnel and equipment. Inparticular, for the steel industry, properly controlled surfacetemperatures result in better quality of steel and increased productionrates.

To minimize breakouts, the conventional wisdom is to follow empiricallyestablished cooling processes that tend to overcool the slab as itpasses through the caster. This is accomplished by controlling the flowof coolant with the assistance of a series of preset flow rates. Thepreset rates are adjusted to achieve an approximate temperature atvarious points along the caster. While slab temperature is sometimeschecked with a measuring device, this device is not integrated into thecoolant control system. It is common to only have a fixed pyrometer atthe exit from the caster prior to the slab being cut. The resulting lackof accurate temperature control during formation of the shell can affectthe product quality because of the inability of the system to follow apreferred cooling rate.

Attempts have been made in the art to address these deficiencies byproviding a feedback mechanism to control the cooling of the slab as itpasses through the caster. For example, U.S. Pat. No. 4,073,332describes such a system. However, such systems suffer from certaindeficiencies. An example of such a deficiency is the lack of temperaturesensors that are suitable for the harsh environment inside of a caster,which tends to be extremely hot with very low visibility and highvibration. This is recognized in part by U.S. Pat. No. 4,073,332 at Col.5, lines 6-10. Moreover, it has been recognized by others that theapproach described in U.S. Pat. No. 4,073,332 is not practicable. Forexample, U.S. Pat. No. 4,699,202 recognizes the deficiencies of U.S.Pat. No. 4,073,332 at Col. 2, lines 8-21 in detail. The specificationsof each of these patents are incorporated by reference herein in theirentireties.

The need to improve the quality and the quantity of continuously castmaterials with reduced down time are drivers in certain metal productionindustries, such as the steel industry. The state of the art still doesnot include a system for actively controlling continuous casting in ameaningful manner to truly maximize yield. There is still a long feltneed in the art for such a system. The present invention provides asolution for these problems.

SUMMARY OF THE INVENTION

The purpose and advantages of the present invention will be set forth inand apparent from the description that follows. Additional advantages ofthe invention will be realized and attained by the methods and systemsparticularly pointed out in the written description and claims hereof,as well as from the appended drawings.

To achieve these and other advantages and in accordance with the purposeof the invention, as embodied herein and broadly described, theinvention includes a system, method and machine readable program fordynamically controlling the casting of a molten metal.

Generally, the system includes an active control feedback system oraspects thereof including a temperature sensing device that iswell-suited for the harsh environment of the interior of a caster.Temperature measurement can be accomplished either by direct contact ornon-contact methods. The system is configured to compare the measuredtemperature with a preferred casting temperature, such as an idealcasting temperature, at a particular point in the casting process. Thetemperature sensing device is operably coupled to a controller thatcontrols a cooling device. The temperature sensing device may beprovided with a purge gas line for removing debris from the area beingmeasured. The cooling device, in turn, modulates a flow of coolant todynamically cool the material being cast. In accordance with oneembodiment of the invention, the cooling device includes a plurality ofnozzles for delivering one or more cooling fluids to the material beingcast. In accordance with a preferred embodiment of the invention, thenozzles deliver a spray comprising water and air. Dynamically deliveringthe coolant to the material in real time in response to temperaturemeasurements of the material optimizes the efficiency of the castingsystem.

In accordance with another aspect of the invention, a method ofcontinuous casting is provided. The method includes providing a casterand feedback system as described herein. The method further includesmeasuring the surface temperature of a stream of material as it exitsthe mold using a temperature sensing means. The measured surfacetemperature is then compared with a predetermined surface temperaturevalue associated with a desired cooling profile. Based on thecomparison, the flow rate of a cooling fluid inside of the caster isadjusted in response to a difference between the measured surfacetemperature and the predetermined surface temperature. Preferably, themetal exits the caster at a temperature that indicates its core has justsolidified.

In accordance with a further aspect of the invention, a machine readableprogram containing instructions for controlling a caster forcontinuously casting a strand of material is provided. The programincludes means for comparing a measured surface temperature of thestrand of material with a predetermined surface temperature wherein thepredetermined surface temperature is associated with a desired coolingprofile. The program also includes means for adjusting the cooling meansinside of the caster in response to a difference between the measuredsurface temperature and the predetermined surface temperature.

In accordance with a further aspect of the invention, the programfurther comprises means for providing individualized control of each ofa plurality of nozzles or banks of nozzles through which cooling fluidis directed inside of the caster. The program may also include means formaintaining a substantially uniform surface temperature across thesurface of the stream of material while it solidifies. Moreover, theprogram can also include means for sensing when a molten core of thestream of material breaks out through a solidified wall of the stream.In accordance with a further aspect of the invention, the machinereadable program can also include means for controlling the speed of thecaster. Means for controlling the surface temperature of the strand ofmaterial can also be provided by varying the speed of the caster. Inaccordance with still a further aspect of the invention, means fordefaulting to a preselected cooling model can be provided in the eventthat a portion of the system fails, such as a temperature sensor orother component.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and are intended toprovide further explanation of the invention claimed.

The accompanying drawings, which are incorporated in and constitute partof this specification, are included to illustrate and provide a furtherunderstanding of the method and system of the invention. Together withthe description, the drawings serve to explain the principles of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of a continuous casting system as is known in theart.

FIG. 2(A) is a diagram of a continuous casting system made in accordancewith the present invention.

FIGS. 2(B)-2(C) are depictions of an exemplary embodiment of a coolingvalve made in accordance with the invention.

FIG. 3 is a flow chart depicting operation of an active feedback controlsystem made in accordance with the present invention.

FIGS. 4(A)-4(B) are views of representative embodiments of temperaturemeasurement devices used in combination with an active feedbackcontinuous casting control system in accordance with the presentinvention.

FIG. 5 is a view of another embodiment of a temperature measurementdevice used in combination with an active feedback continuous castingcontrol system in accordance with the present invention.

FIG. 6 is a view of an embodiment of a temperature measurement deviceused in combination with an active feedback continuous casting controlsystem in accordance with the present invention, including a rolleradapted to roll against a material as it is being cast.

FIGS. 7-11 are views of embodiments of a temperature measurement deviceused in combination with an active feedback continuous casting controlsystem in accordance with the present invention, including a member insliding engagement with material as it is being cast.

FIGS. 12(A)-12(B) are views of embodiments of a temperature measurementdevice used in combination with an active feedback continuous castingcontrol system in accordance with the present invention, including apyrometer.

FIGS. 13(A)-13(J) are views of embodiments of temperature measurementdevices used in combination with an active feedback continuous castingcontrol system in accordance with the present invention, utilizing airflows to facilitate temperature measurement, or aspects thereof.

FIG. 14 is a view of an embodiment of a temperature measurement deviceused in combination with an active feedback continuous casting controlsystem in accordance with the present invention, utilizing electricaltechniques.

FIG. 15 is a view of an embodiment of a temperature measurement deviceused in combination with an active feedback continuous casting controlsystem in accordance with the present invention, including spectroscopictechniques.

FIG. 16 is a view of an embodiment of a temperature measurement deviceused in combination with an active feedback continuous casting controlsystem in accordance with the present invention, including a heat fluxsensor.

FIG. 17 compares an actual cooling curve for steel with an exemplaryideal cooling curve.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Reference will now be made in detail to the present preferredembodiments of the invention, an example of which is illustrated in theaccompanying drawings. The method and corresponding steps of theinvention will be described in conjunction with the detailed descriptionof the system. The systems and methods presented herein may be used forcasting metals. The present invention is particularly suited forcontinuous casting of steel and steel alloys.

For purpose of explanation and illustration, and not limitation, aschematic view of an exemplary embodiment of the system made inaccordance with the invention is shown in FIG. 2(A) and is designatedgenerally by reference character 100. Other embodiments of a system inaccordance with the invention, or aspects thereof, are provided in FIGS.2(B)-16, as will be described.

In accordance with the invention, a system is provided for dynamicallycontrolling the casting of a material. The system is adapted andconfigured to dynamically cool and solidify a stream of material beingcast in accordance with a predefined cooling profile.

For purposes of illustration and not limitation, as embodied herein andas depicted in FIG. 2(A), system 100 includes a caster 10 that isadapted and configured to continuously cast a slab 140 of material, suchas a metallic material. It will be understood that slab 140 can take onvarious other names such as a strand and the like, depending on theapplication. Caster 10 includes a first end or entrance 112 where moltenmaterial 10 is poured by a ladle 20 into a tundish 120. Tundish 120 actsas a reservoir for storing molten material 10 and includes an interiorsurface 122 that terminates in a mold 124. As material 10 is directedthrough tundish 120, a primary cooling system 130 removes heat frommaterial 10 until a solidified skin forms on the material 10, resultingin a partially solidified slab 140 as material 10 exits the mold 124.

After exiting mold 124 within caster 110, slab 140 is guided through aplurality of caster segments 150 from a generally vertical direction toa generally horizontal direction. Slab 140 is guided by a plurality ofrollers 160 within the caster segments 150. As slab 140 passes throughcaster 110, it is also cooled by a cooling means 170. Slab 140 ispreferably cooled at a rate sufficiently high to maintain the thicknessof the skin of slab 140 to prevent breakout, but sufficiently slow toprevent slab 140 from solidifying too quickly. Preventing overcooling ofslab 140 reduces wear and vibration on rollers 160 and other portions ofcaster 110. When slab 140 has exited the caster 110 at caster exit 114,slab 140 has preferably been cooled to the point that it is solidthroughout its cross section. After exiting caster 110, slab 140 is cutinto predetermined lengths by a cutting mechanism 300. Each of theseelements is discussed in further detail below.

While a horizontal caster 110 is depicted in FIG. 2(A), it will beunderstood that a variety of casting configurations can be used inaccordance with the invention. For example, vertical casters can also beused. To illustrate this difference, in a horizontal casting machine asdepicted in FIG. 2(A), the slab 140 exits the mould vertically and as ittravels through the casting segments 150, the rollers 160 graduallycurve the slab 140 towards the horizontal. By contrast, in a verticalcaster, the slab 140 stays vertical as it is cooled.

It will be understood that caster 110 can be used to continuously cast avariety of materials 10, such as metallic materials. Specifically,caster 110 can be used to cast a wide variety of steel grades, otherferrous and non ferrous materials and the like. Moreover, virtually anymold 124 can be used as are known in the art. Mold 124 can have a crosssection of a variety of shapes, including circular, ovoid, rectangular,“I” shaped and the like, as desired. Primary cooling system 130 includesa heat exchanger that is adapted and configured to remove heat frommaterial 10 by way of fluid flow through a plurality of passages formedwithin or adjacent to tundish 120 and mold 124.

Any suitable number of caster segments 150 can be used. Generally,anywhere between four and eight caster segments can be suitable,depending on the material being cast, and the rate at which it isdesired to cool the slab 140. Rollers 160 can be similar to those knownin the art of casting. As depicted in FIG. 4(A), roller 160 includes anouter surface 162 defined by a width 164 and a circumference 166. Eachroller 160 is supported by bearings at each end 168. The structure andmaterials of roller 160 are well known and are not repeated herein.

In further accordance with the invention, a cooling means is providedthat is adapted and configured to dynamically cool and solidify thestrand of material. As discussed herein, there is a long felt andunresolved need in the art for a cooling means including a practical andeffective temperature measurement system for accurately measuring thesurface temperature of a slab of material while inside of a caster. Thepresent invention provides a plurality of novel solutions for thisproblem.

For purposes of illustration and not limitation, as depicted in FIG.2(A), a cooling means 170 is provided as mentioned above. Cooling means170 includes temperature measurement devices 180 that are operablycoupled to a control system 190 (schematically depicted in FIGS. 2 and 3and discussed in detail below) for dynamically controlling a pluralityof cooling devices such as cooling nozzles 200, to dynamically cool theslab 140 of material as it passes through the caster. In accordance witha preferred embodiment, slab 140 is cooled in accordance with apredefined cooling profile before exiting the caster. In accordance withone embodiment, temperature measurement device 180 is adapted andconfigured to measure the temperature of slab 140 from the time it exitsthe mold 124 until it exits leaves the caster 110 at caster exit 114.

In accordance with one aspect of the invention, the temperaturemeasurement devices 180 measure the temperature of the slab by way ofdirect physical contact.

For purposes of illustration and not limitation, as depicted in FIG. 4A,a first representative embodiment of a temperature measurement device180 includes a device, such as a thermocouple 182, that is placedproximate the surface 162 of inside of a roller 160 as described herein.Thermocouple 182 can be placed on or immediately beneath the surface 162of the roller to obtain a correlatable and real-time measurement of thesurface 142 of slab 140 as the slab 140 rolls along roller 160.Moreover, a plurality of thermocouples 182 can be placed on or beneaththe surface 162 of roller to provide discrete temperature measurementsalong the width 164 of roller as well as the circumference 166 of roller160. Temperature measurement data collected by thermocouples 182 can befed by one or more data transmission lines 192 into control system 190.Commutators 161 can be used at each end 163 of roller 160 to provide alink for signal transmission.

In accordance with an alternative embodiment, as depicted in FIG. 4B, aresistance temperature detector (“RTD”) or temperature sensitivecapacitor (“TSC”) 186 can be operably coupled to a resonant circuit 187embedded in the roller 160. As depicted, resonant circuit 187 caninclude a conductive winding 187(a) that is adapted and configured tocouple with an electromagnetic wave 187(b) launched from a source suchas a launching antenna 189 at a predetermined frequency. Once energized,circuit 187 can apply current across RTD or TSC 186 to generate a signalindicative of the temperature at that location. Resonant circuit 187then broadcasts a signal 187(c) including the temperature information.As will be appreciated by those skilled in the art, resonant circuit 187will have a resonant range over which it can receive and transmitradiation. In accordance with one embodiment, the resonant circuit hasan operative range between about 14 MHz and 16 MHz. By scanning over afrequency range that includes these frequencies, such as from 10-20 MHz,it is possible to detect the signal emitted by the resonant circuit 187.

Alternatively, as depicted in FIG. 5, optical techniques can be used tomeasure the temperature on the inside surface of the roller 160 (or thesurface of slab 140 itself through an aperture 160 a defined in theroller), such as a pyrometer 280 that detects radiation from a pointinside roller 160 through a fiber optic cable 282 and out through end163 of roller by way of an optical commutator 284. Optical commutator284 can take on a variety of forms. While one light path 285 could beprovided through end 163 of roller 160 for measuring a single locationinside roller 160, a plurality of fiber optic lines 282(a)-(n) can bedisposed radially outwardly from the center of roller 160 such that theend 284(a)-(n) of each fiber optic line 282 at end 163 of rollercompletes a light path once per revolution of roller 160. The fiberoptic line 282 connected to each end 288 can be directed to measuretemperatures at different points 287 across the width of the roller 160in order to obtain a temperature profile across the width of the slab140.

By way of further example, as depicted in FIG. 6, temperaturemeasurement device 380 can include a roller 382 that is adapted andconfigured to selectively roll along slab 140. Roller 382 is disposed ata first end 392 of a beam 390. Beam 390 further includes a second end394 and defines a pivot point 396 between the first end 392 and secondend 394 of beam. A pin 398 pivotally connects beam 390 to caster 110. Asdepicted, beam 390 is located between adjacent rollers 160. A spring 400connects second end 394 of beam 390 to the caster 110. Spring 400 isadapted and configured to urge roller 382 against slab 140 to facilitatetemperature measurement thereof.

Roller 382 is rotatably mounted on an axle 384. Roller 382 can be madefrom a refractory material, such as a ceramic material or othermaterials, such as silicon carbide or alumina. Axle 384 contains athermocouple 386 that is operably coupled to a signal line 388 thatdirects temperature measurements of slab 140 to control system 190.While thermocouple 386 actually measures the temperature inside of axle384, temperature measurement device 380 is appropriately calibrated toindicate the surface temperature of slab 140 based on the measurementinside of axle 384. A purge gas flow may be applied to the wheel thatreduces the error due to convection of water and steam, such as by wayof purge gas channel 400 a that surrounds beam 390 fed by gas supplyline 400. In accordance with one embodiment, the thermocouple 386 isinsulated inside of axle 384.

In accordance with a further alternative embodiment, as depicted in FIG.7 temperature measurement device 480 is adapted and configured to slideagainst slab 140. As depicted, a skid 482 is provided at first end 492of beam 490. As with the embodiment of FIG. 6, beam 490 further includesa second end 494 and defines a pivot point 496 between first end 492 andsecond end 494 of the beam, and pin 498 pivotally connects beam 490 tocaster 110. As with the embodiment of FIG. 6, spring 400 is adapted andconfigured to urge skid 482 against slab 140 to facilitate temperaturemeasurement thereof. Skid 482 can be made from ceramic material and havea thermocouple 486 disposed therein. As with the embodiment of FIG. 6,temperature measurement device 480 can be calibrated to correlate thetemperature measured by thermocouple 486 with the actual surfacetemperature of slab 140. A purge air flow may be applied to the wheelthat reduces the error due to convection of water and steam as with theembodiment of FIG. 6.

In further accordance with the invention, other embodiments of atemperature measurement device configured and adapted to drag againstthe surface of slab can also be used.

For purposes of illustration and not limitation, as depicted in FIG. 8,a temperature measurement device 580 is integrated into the structure ofthe caster 110. The structure of caster 110 can include a grid structure582 defining a plurality of cavities 589. Cavities provide a spacewithin which cooling sprays can flow to cool slab 140. Grid 582 can beprovided with a face plate 584 that is adapted and configured to contactslab 140. A cavity 585 can be defined within grid 582 for housing athermocouple assembly 586. If desired, thermocouple assembly 586 can bebiased by a spring 588 against face plate 584 to improve thermalcommunication therewith. Face plate 584 is preferably formed from amaterial having a surface suitable for high temperature use. Grid 582can be made from a variety of materials, such as copper alloys, beryllia(beryllium oxide), graphite and the like.

As depicted in FIG. 9, thermocouple assembly 586 can include a hightemperature tip 590 fixedly attached to a tube 592 housing thermocouplewires 594. A threaded mount 596 can be provided into which ceramic tube592 is inserted. If desired, threaded mount 596 can include threads (notshown) that are adapted and configured to cooperate with threads formedin housing 582 to facilitate installation and removal of thermocoupleassembly 586. Ceramic tube 592 can be provided with a shoulder 593. Asdepicted, spring 588 pushes against shoulder 593 and mount 596 to causethermocouple assembly 586 to urge against face plate 584.

In accordance with another embodiment, as depicted in FIG. 10,temperature measurement device 680 is provided comprising a consumablethermocouple 686. As depicted in FIG. 10, consumable thermocouple 686includes a generally tubular housing 682 that is preferably made from ametallic material. Housing 682 surrounds the operative portion ofconsumable thermocouple 686, which includes thermocouple wires 684,disposed in an erodable medium 688. Exposed end 690 of device 680 isurged into direct contact with the surface of slab 140 by urging means692. In operation, a circuit is completed between wires 684, 686 throughslab 140. Wires 684, 686 should be maintained in continuous contact withslab to permit continuous operation of device 680. It will be understoodthat measurements obtained from device 680 will vary depending on theenvironment in which the device is being operated. As such, it will benecessary to calibrate device 680 in order to correlate signals fromdevice 680 with a given surface temperature of slab 140. As slab 140passes over temperature measurement device 680, end 690 of device slowlyerodes, consuming the material of the thermocouple. Urging means 692 cantake on a variety of forms as disclosed herein. A purge gas, such asair, may be applied inside tubular housing 682 by way of source line 600b to reduce convective effect of water and steam.

In accordance with another embodiment, as depicted in FIG. 11,temperature measurement device 780 can include a resilient housing, suchas a tubular member 782 made from or coated with silicon carbide andhousing a thermocouple 786. Signals indicative of heat detected bythermocouple 786 are accordingly transmitted through control system 190.Device 780 can be urged in sliding engagement with slab 140 by an urgingmeans 792 such as those described herein. If desired, the contactbetween temperature measurement device and slab can be periodic. Forexample, a spring loaded temperature sensor can contact the slab everyfew seconds for a short period of time. This can extend the life of thetemperature measurement device used. A purge gas flow may be applied asshown via conduit 700 a and source line 700 b to reduce the effects ofwater and steam.

In accordance with still a further aspect of the invention, thetemperature sensing device is configured and adapted to measure thesurface temperature of the material without physically contacting thematerial.

For purposes of illustration and not limitation, as embodied herein andas depicted in FIG. 12(A), temperature measurement device is provided inthe form of a pyrometer 880 that is adapted and configured to view thesurface of slab 140 to measure the temperature thereof. Pyrometer 880includes an optical system having a field of view 882. If desired, purgeair for cleaning pyrometer and preventing overheating can be provided byway of a purge line 884. Also, the purge tube shown can be used toprevent water and steam from impeding the radiation.

Suitable pyrometers 880 are disclosed in U.S. Patent Publication No.2005/0247066A1 and U.S. Patent Publication No. 2006/0000219A1 and U.S.Pat. No. 4,521,088, each of which is incorporated by reference herein inits entirety. Pyrometer 880 can be adapted and configured to scan acrossthe surface of slab 140 to obtain a temperature profile across the widthof slab 140. In accordance with one embodiment, an active millimeterwave pyrometer can be employed made in accordance with the teachings inU.S. Pat. No. 5,785,426, which is incorporated by reference herein inits entirety. Pyrometer 580 can also be added downstream in the caster110 at the edge of the slab 140 to measure the surface temperature atthe slab edge. Such a construction may be used to detect cracks at theedge of slab 140, since cracking causes sharp changes in the emissivityof the surface of the slab which are detected by the pyrometer.

FIG. 12(B) depicts a method for holding the pyrometer in the caster byutilizing the cooling nozzle for a convenient attachment. Also, magneticclamps 1200 a may be used to hold the pyrometer on the caster in anyposition due the fact they are made from steel.

By way of still further example and as depicted in FIG. 13(A), atemperature sensor 980 (such as pyrometer 880) can be mounted close tothe moving slab in operable communication with an air nozzle 982 adaptedand configured to provide an air jacket 984. Air jacket 984 acts toprevent overheating of sensor 980, and helps prevent sensor 980 frombecoming fouled, as well as maintaining clarity of the radiation pathsubstantially free of debris. Further details on such sensors aredescribed in U.S. Pat. No. 5,146,244, U.S. Pat. No. 4,836,689 and U.S.Pat. No. 4,786,188, the disclosure of each being incorporated byreference herein in its entirety.

By way of further example, the temperature of the surface of slab 140 ismeasured by measuring the temperature of air proximate the surface ofthe slab. For purposes of illustration and not limitation, as embodiedherein and as depicted in FIG. 13(B), temperature measurement device1080 includes a housing 1082 defining a flow passage 1084 having a firstend 1083 and a second end 1085 in which one or more thermocouples 1086are disposed. Flow is induced through first end 1083 and into passage1084 to cause air or other gas proximate surface of slab 140 to be drawnthrough passage 1084 and over thermocouple 1086 and then at the secondend 1085 to obtain an estimate of the temperature of slab 140. Flow canbe induced through passage 1084 in a variety of ways as are known in theart. For example, a Venturi pump 1090 can be fluidly attached to secondend 1085 of passage 1084. A high speed gas jet 1092(a) can then bedirected through passage 1092 of pump 1090 to induce flow 1084(a)through passage 1084. Venturi pumps such as pump 1090 are commonly madefrom materials such as steel and the like.

By way of still further example, as depicted in FIG. 13(C), atemperature sensor 1800 may be provided including a photon sensingdevice, such as a pyrometer that is adapted and configured to measurethe temperature of the slab 140 by characterizing the energy of photonsreceived from the slab 140. More specifically, temperature sensor 1800includes an extended tubular member or hollow tubular member or conduit1820, having a first end 1822 and a second end 1824 to permit passage ofphotons emitted by the surface of slab 140 to a lens 1830. Photons arethen focused on a photon sensor 1840, such as a photodiode to generateelectrical signals processed by electronics 1850 that are output viacable 1860 to the control system as described herein. A compressed gasinput 1870 is provided to direct purge gas across lens 1830 to keep lens1830 clean, and to maintain the radiation path between lens 1830 andslab 140 substantially clear.

Tubular member 1820 may have any suitable dimensions. Generally, it isdesired that the gas purge discharged second end 1822 of tubular member1820 have a sufficiently high velocity to clear debris (e.g., steam andwater) from the line of sight of lens 1830. Preferably, the average gasvelocity is greater than about 100 feet per second. More preferably, theaverage gas velocity is greater than about 200 feet per second or more.

It will be further appreciated that the gas purge may be sent down thepassage 1826 of member 1820, and/or down one or more supplemental purgelines 1828. Specifically, by using supplemental purge lines 1828 it ispossible to eject a high speed flow in the viewing area while minimizingthe volume flow rate of the purge gas. Moreover, while a gas purge canstill be directed through passage 1826, such a flow can be used toprimarily cool the passage and upstream optics and electronics. Such anarrangement also permits the diameter of passage 1826 to be increased tocollect additional photons but without significantly increasing the needfor a purge gas flow.

In accordance with one embodiment that was tested, the dimensions of thetubular member 1820 was 2 feet long by 0.9 inch inside diameter pipe (¾″schedule 10 pipe). A single lens 1830 was employed having a two (2) inchfocal length to collect radiation passing through passage 1826 andfocusing it on the photon sensor 1840. The length of the extension waschosen primarily based on practical considerations of the particulartesting application. For example, clearances in the caster 110 may guidethe choice of certain dimensions. However, it will be appreciated thattubular member 1820 may be of any suitable length. Generally, a shortprobe may be more difficult for an installer to reach in and secure.Also, the closer the optics and electronics are to the steel slab 140,the greater is the risk of thermal effects on the electronics. Moreover,if a break out of the molten core of the slab 140 were to occur, it islikely that more damage could occur to the sensor 1800. The purge gaswas air supplied from a compressed air source at a line pressure ofabout 90 pounds per square inch.

In accordance with one embodiment, first end 1822 of conduit 1820 may becut on an angle to cause the purge gas to blow debris (e.g., soot, waterand steam) out of the field of view of lens 1830. Using an extendedconduit with a gas purge as described herein has been found to beeffective in maintaining a clear radiation path between the slab and thephoton sensing device. Specifically, upstream portions of a caster nearthe mold are the hottest, and the most occluded by steam, water andsoot.

However, use of a sensor such as 1800 avoids these problems. Moreover,spacing the photon sensing device portion of the sensor a distance fromthe slab also has the benefit of exposing the electronics to a lessharsh environment.

As further depicted in FIG. 13(C), first end 1822 of tubular member 1820is angled. In the depicted embodiment, the angulation is achieved bycutting end 1822 at an angle, such as about 10 degrees from an axisperpendicular to a longitudinal axis defined by the tubular member. Thisangulation effectively causes flow to be directed in the direction ofthe shallow end of the cut as it exits the tubular member. This helpsclear debris from the viewing area of the sensor.

As will be appreciated, for any of the embodiments disclosed hereinutilizing an optical pyrometer as a device to measure the temperature ofslab 140 (including but not limited to sensor 1800), a variety ofoptical pyrometers may be used. For example, a pyrometer may be used inany suitable region of the spectrum. For example, a pyrometer may beused that is particularly sensitive to the ultraviolet (“UV”) region ofthe spectrum. In accordance with one embodiment, a UV pyrometer may beused that is sensitive to wavelengths shorter than about 0.5 microns,such as from about 0.35 microns to about 0.45 microns. These wavelengthsare relatively high energy wavelengths and are more effective atpenetrating the harsh environment of a caster to reach a pyrometer.Moreover, such wavelengths appear to be well suited for measuring thetemperature of oxidized steel (about 1700° F.-about 2100° F.), and areless susceptible to error as a result of slag formation on the surfaceof slab, which is a random occurrence. However, a NIR pyrometer whenused with a gas purge as described herein also provides successfulresults.

Water absorption of photons is a problem because of the water used tospray the surface of slab 140 to cool the slab creates an absorptionbarrier between the pyrometer and the slab. For example, FIG. 13(D)depicts the absorptivity bands (in terms of transmission) for watervapor.

Variable emissivity is another problem endue to the slag that forms onthe slab surface causing the emissivity to vary significantly. Slag andbare metal vary in emissivity with wavelength and temperature. Theemissivity of such oxidized surfaces is typically 0.9 to 0.96. Toillustrate the accuracy of UV temperature measurement, a test was runusing a piece of carbon steel that was heated on one side using anoxyacetylene torch as depicted in FIG. 13(E). The temperature of thesteel was measured with a type B thermocouple and a pyrometer on theside opposite the torch. The data collected is shown in FIG. 13(F). Thepyrometer utilized a silicon photodiode that was filtered to detectwavelengths from about 0.35 micron to about 0.45 micron. Based on theseresults, it can be determined that this spectral range is favorable formeasuring oxidized steel and can easily be corrected for the averageemissivity over the temperature of use with only a small effect on theaccuracy. The emissivity of slag on a surface of a steel strand variesleast from the steel at these shorter wavelengths. As such, measurementof photons emitted by slab 140 at shorter wavelengths can be expected togive less temperature error when the pyrometer is observing steel orslag.

Moreover, a two color pyrometer may be used to obtain an accuratesurface temperature measurement. A two color pyrometer makesmeasurements in two wavelength regions and electronically takes theratio of these measurements. A preferred embodiment would have aspectrum covering wavelengths from 300 nm to 500 nm and another spectrumcovering 300 nm to 1000 nm, as depicted in FIG. 13(G). The primaryadvantage of the two color (or spectrum) pyrometer is its ability tocancel out the emissivity of the measured surface for improved accuracy.If the emittance is the same for both wavelengths, the emittance cancelsout of the result, and the true temperature of the target is obtained.It is believed that this gray-body assumption is sufficiently valid inthe context of the present invention to provide a “color temperature”measured by a two color pyrometer that is close to the true temperatureof slab 140. Preferably, at least one of the wavelengths detected by thetwo color pyrometer is in a UV wavelength range as described herein.

EXAMPLE Testing of In Situ UV Pyrometer and Two-Color Pyrometer

Testing was performed at a steel mill during a continuous castingprocess. The test employed a temperature sensor similar to sensor 1800described above including a UV pyrometer to measure the steeltemperature. A NIR (near infrared) pyrometer was also mounted at thesame location with a tubular member having a gas purge as describedherein. Data was examined to compare the accuracy of the spectraobtained from the two pyrometers.

The UV pyrometer utilized silicon photodiodes as photon sensors. Two ofthe photodiodes were filtered with a color glass filter. This provided auseable spectrum of about 350 nm to 450 nm, well overlapping the UVportion of the electromagnetic spectrum. The NIR pyrometer was aGoodrich production model modified to include a purge line. The NIRpyrometer uses a silicon photodiode that is not filtered. It has astandard silicon responsivity with a peak sensitivity at about 850 nm.

FIG. 13(H) depicts the output data taken for a period of time. The NIRtemperature profile is the lowest temperature profile. The UV pyrometerprofile is the temperature profile in the middle, and a calculatedtwo-color temperature is the top temperature profile. As can be seen,the measured temperature of the UV pyrometer was significantly closer tothe true temperature than the NIR pyrometer.

Curve fit equations for each pyrometer in this example can berepresented as:

T ₁ =A ₁(E ₁ g)^(B1)   (1)

T ₂ =A ₂(E ₂ g)^(B2)   (2)

A and B are curve fit constants and “g” represents the gain needed tomake the temperatures T₁ and T₂ equal (1/emissivity). E₁ and E₂ arepyrometer outputs. Setting temperatures equal and solving for g:

g=(A ₁ E ₁ ^(B1)/(A ₂ E ₂ ^(B2)))^((1(B2−B1)))   (3)

Therefore, the if the gain correction is solved at each data point thecorrected temperatures can be solved for at each point. This was plottedin FIG. 13(H) as the uppermost data set. For this particular example,the gain correction averages 7.13 which equates to an average emissivityof 0.14.

Still another embodiment of a temperature measurement device 2800 isdepicted in FIG. 13(I) having an elongate tubular member 2820 with afirst end 2822 and a second end 2824 secured to a housing 2860. Device2800 operates similarly to device 1800, in that both devices use a purgegas in combination with a pyrometer. FIG. 13(J) depicts a magnifiedcross sectional view of the housing portion 2860 of device 2800. Asdepicted, second end 2824 of tubular member 2820 is connected to a firstend cap 2862 of housing 2860. Housing further includes a second end cap2864, and a generally cylindrical wall 2866 disposed between end caps2862, 2864. The housing assembly is held together by a plurality ofbolts 2867 and nuts 2868.

Inside housing 2860, an intermediate electronics compartment 2850 isdefined having an electronics board 2852 disposed therein operablycoupled to a sensor 2846, such as a photodiode. Electronics board 2852,in turn, is attached to a connector 2880 to direct signals out of device2800 to a terminal location, such as a computer (not shown). Electronicscompartment 2850 is attached at a first end 2854 to end cap 2864 and ata second end 2856 to a sensor housing 2840. First end 2842 of sensorhousing 2840 houses a lens 2830 held in place with a clip (not shown)and an o-ring 2845. Sensor 2846 is disposed in a second end 2844 ofsensor housing 2840. A plurality of struts or spacers 2848 space housing2840 from end cap 2862 to define a plurality of gas purge passages 2874.Purge gas is provided through purge inlet 2870 and directed throughannular space 2782 defined between wall 2866 and housing 2850, throughpassages 2874 and through tubular member 2820. Such a gas flowarrangement helps cool the optics and electronics in device 2800.Moreover, as will be appreciated, such an arrangement greatlyfacilitates maintenance of device 2800. For example, housing 2860 ofdevice 2800 may be disposed outside of the caster and tubular member2820 may protrude through a wall of the caster. To perform maintenanceon the contents of housing 2860, all a technician need do is remove nuts2868 and pull out the assembly including electronics housing 2850 andsensor housing 2840.

In accordance with another embodiment, as depicted in FIG. 14,temperature measurement device 1280 includes means for measuring theelectrical conductivity of the slab 140. For example, as depicted inFIG. 14, electrodes 1282 can be provided that are adapted and configuredto contact the surface of slab 140. Preferably, the electrodes 1282include tips made from a hardened refractory material, such as tungsten,so that they penetrate the surface of slab 140 to ensure constantelectrical communication therewith. A voltage is imposed across theelectrodes 1282 through the slab 140 to measure the conductivity of theslab. Based on electrical measurements, it is possible to compute theelectrical resistivity of slab 140. Electrical resistivity is a knownfunction of temperature for different materials. Thus, based on aresistivity measurement, it is possible to measure the temperature ofthe slab based on known values of electrical resistivity as a functionof temperature.

Moreover, if desired, an array of electrodes 1282 can be provided with aswitching mechanism 1284 to obtain conductivity measurements acrossdifferent portions of the surface of the slab, such as betweenelectrodes 1282(a) and 1282 (b), or through the slab such as betweenelectrodes 1282(a) and 1282(c). It will be appreciated by those skilledin the art that any suitable number of electrodes can be used andpositioned as desired to obtain as many different conductivitymeasurements and hence, temperature measurements as desired.

In accordance with still another aspect, the temperature of the slab canbe sensed using phosphor thermometric techniques. For purposes ofillustration and not limitation, as embodied herein, it is possible tomeasure the temperature of slab 140 by employing one of a variety ofthermographic techniques. For example, such surface measurementtechniques are described in literature published by Oak Ridge NationalLaboratory (see http://www.ornl.gov/sci/phosphors/galv.htm). Systemsemploying such methods to measure the temperature of materials such as amoving substrate are described, for example, in U.S. Pat. No. 6,123,455,U.S. Pat. No. 5,986,272, and U.S. Pat. No. 5,949,539, the disclosure ofeach of which is incorporated by reference herein in its entirety.

As depicted in FIG. 15, once the phosphor material is introduced ontothe molten metal, the light level emitted can be viewed, for example,with a temperature measurement device 1380 comprising a spectrometer.This can be accomplished, for example, by viewing the light emitted bythe trace element with a lens 1382, and directing the light throughfiber optic lines 1384 to a spectrometer 1386, wherein the spectrum isseparated using a grating 1388 to permit observation of the atomictransitions of the trace elements via a photodetector array 1390operably coupled to a graphical user interface 1392, such as a personalcomputer. For example, a Time Rate of Decay (TRD) method can be used tomeasure temperature. In a TRD method, pulses of a fluorescent materialare injected into the cooling spray. Fluorescing material will emitradiation at different energies (having a specific wavelength) dependingupon temperature of the fluorescing material. Accordingly, it ispossible to determine the temperature near the slab surface bycorrelating the wavelength rate of change of the intensity of theradiating fluorescing material with a temperature. Thus, a temperatureprofile of slab 140 may be obtained by viewing the change in theemission of the phosphor coating.

In accordance with an alternative embodiment, if desired, one or morerollers 160 can be coated with a coating that emits light in accordancewith its temperature. Suitable coatings include thermographic phosphorsand other temperature sensitive coatings. As with the previouslydescribed technique, emitted light can be viewed and processed toestimate the temperature of the surface of slab 140.

In accordance with still another aspect, the temperature of the slab canbe sensed by measuring heat flux.

For purposes of illustration and not limitation, as embodied herein andas depicted in FIG. 16, temperature sensing device 1480 employs a heatflux sensor 1482 to detect heat given off by slab 140. Heat flux sensorsare known in the art, and generally comprise two thermocouples 1486separated by a material of known thermal conductivity 1488. It will beunderstood that the measured heat flux can be empirically correlated toa surface temperature of the slab. The configuration of FIG. 7 couldalso be used as a heat flux sensor with the thermocouple replaced with aheat flux sensor.

In further accordance with the system of the invention, the coolingmeans includes a coolant delivery system such as nozzles for deliveringcoolant to the slab. For purposes of illustration and not limitation, asdepicted in FIG. 2(A), cooling devices such as nozzles 200 can directcoolant such as water, or a mixture of water and air toward slab 140.Suitable nozzles are described, for example, in U.S. Pat. No. 6,036,116,U.S. Pat. No. 6,729,562, U.S. Pat. No. 6,578,777, and U.S. patentapplication Ser. No. 11/736,810, filed 18 Apr. 2007, among others. Eachof these documents is incorporated by reference herein in its entirety.Nozzles 200 can be arranged in any suitable configuration inside ofcaster segments 150. In accordance with a preferred embodiment, nozzles200 are arranged individually or in banks across the width of the slab140. In accordance with another embodiment, each nozzle 200 is providedwith an individually controllable valve 210. Suitable valves include,for example, solenoid controlled valves, or a valve adapted andconfigured for air actuator control in conjunction with an electricalsolenoid or electrical motorized actuator control. The valve structurescan comprise ball valves or butterfly valves, for example. Suitablevalves can be obtained, for example, from Fisher Controls International,LLC (301 S. 1st Avenue, Marshalltown, Iowa 50158). Alternatively, ifdesired, a plurality of nozzles, such as an entire bank of nozzles(e.g., disposed across the casting segment 150) can be controlled usinga single control valve 210. As such, the valve bank can be configured todeliver a varying amount of coolant across the width of slab 140, suchas by delivering more coolant to the middle of the slab as contrastedwith the edge to ensure even cooling. It will be understood that thesystem can be adapted to provide flexibility for the control system 190to allow control of individual nozzles or any number of spray nozzles,zones of nozzles, and manifold sections of nozzles or caster segments ofnozzles with any number of reliable temperature measuring devices foraccurate control.

FIG. 2(B) illustrates another spray nozzle in accordance with anembodiment of the invention. The arrangement of the spray nozzle of FIG.2(B) comprises a nozzle body 40 to which an air inlet 42 is connected bya screw threaded connection. The air inlet 42, in turn, is connected toan air supply line 44. The air inlet 42 locates, within the nozzle body40, an air orifice member 46. For convenience, the nozzle body 40 is oftwo-part form, comprising parts 40 a and 40 b but this need not alwaysbe the case. The part 40 b further serves as a connector to which alance 62 (discussed below) is secured.

The nozzle body 40 further includes a water inlet port 48 to which awater inlet member 50 is secured by a screw-threaded connection, thewater inlet member 50 being secured to a water supply line 52.

The nozzle body 40 is formed with a passage 54 in which is located awater orifice member 56 to convey water from the water inlet port 48 toan annular chamber 58 defined around the air orifice member 46. Waterfrom the chamber 58 is able to flow through a cross-slot 46a to a mixingzone 60 where the air flow forms the water into a mist of waterdroplets, the mist of water droplets being conveyed along the lance 62and through a spray head 64 to the desired location.

The water orifice body 56 comprises a substantially cylindrical body,part 56 a of which is formed with screw-thread formations to allow thewater orifice body 56 to be secured within the passage 54 formed in thenozzle body 40. The water orifice body 56 is formed with a through bore66 shaped to define a region 68 of reduced diameter forming an orificeor restriction to the rate at which water can flow through the orificebody 56. The through bore 66 is closed, at its end remote from theregion 68 by an access cap 70 which is securable in position by ascrew-threaded connection. The water orifice body 56 further includes awater inlet port 72 defined by a passage perpendicular to, andcommunicating with, the through bore 66.

In order to minimize or prevent leakage of water between the nozzle body40 and the water orifice member 56, a deformable sealing washer 74(made, for example, from copper) is conveniently trapped therebetween.

In use, with the spray nozzle connected to the air and water supplylines 44, 52 as illustrated, water is supplied to the inlet port 48 ofthe nozzle body 40 to the water orifice member 56 from where it flowsalong the through bore 66 and through the region 68 to the annularchamber 58. From the annular chamber 58, water is able to flow throughthe cross-slot 46 a to the mixing zone 60 where the action of the airsupplied through the air orifice member 46 causes the water to atomizeand form a mist of water droplets. The mist of water droplets is carriedthrough the lance 62 to be delivered by the head 64 in the desiredlocation and in the desired pattern.

In the event that a blockage forms in the through bore 66 formed in thewater orifice member 56, rather than requiring the nozzle to be totallyremoved and dismantled, the access cap 70 can be removed from the waterorifice body 56, and compressed air supplied to the through bore 66. Theaction of applying the compressed air will typically clear the blockagethus, once the access cap 70 has been re-secured in position, normaloperation of the spray nozzle can continue. In the event that theapplication of compressed air to the through bore 66 in this manner isunsuccessful in clearing the blockage, then the water orifice body 56can be removed from the remainder of the spray nozzle to permitcleaning, replacement or servicing thereof again without requiringremoval of the complete spray nozzle. After cleaning of the waterorifice body 56, it can be returned to its operative position as shownin FIG. 2(B), typically with the sealing washer 74 having been replacedin order to maintain the integrity of the seal between the water orificebody 56 and nozzle body 40. It will be appreciated that both of theseoperations can be conducted without disconnecting the nozzle from thewater and air supply lines, and so can be conducted relatively quicklyand with minimum disruption to the production process.

A further advantage of the arrangement illustrated in FIG. 2(B) ascompared to conventional arrangements is that, in the event that it isdesired to vary the rate at which the mist of water droplets isdelivered, this can be achieved by replacing the water orifice body 56with one having a region 68 of a different diameter. Again, clearly thiscan be achieved without requiring replacement of the entire spraynozzle.

The arrangement described herein for nozzle 200 may be used in otherways as well. For example, rather than providing an access cap 70 toclose the end of the through bore 66, a further inlet line could beconnected thereto. One possibility is to connect an additional air linethereto. This has the advantage that, by appropriate control over thepressure of the additional air line, the water supply rate can bechanged without having to adjust its supply pressure. Further, the wateris, at least partially, atomized prior to reaching the mixing zone 60,thereby permitting the nozzle to be used in the formation of a spray ofreduced droplet size compared to typical arrangements.

The nozzle may be modified to orientate the water inlet port 72 suchthat it is tangential to the through bore 66, thereby imparting aswirling motion to the water, as shown in FIG. 2(C). The formation of aswirling motion in the water results in the water passing through theregion 68 in the form of a hollow conical spray. Consequently, the sizeof the region 68 can be increased, leading to a reduction in the risk ofit becoming blocked, without resulting in an increase in the rate atwhich water passes through the region 68.

In further accordance with the invention, a control system is providedoperably coupled to the cooling means and the temperature sensing means.The control system is adapted and configured to control the coolingsystem to cool the material as it passes through the caster. Forpurposes of illustration and not limitation, as embodied herein and asdepicted in FIG. 3, a control system 190 is provided to control thecooling of slab 140 as it passes through caster 110. Control system 190includes a processor 194 provided, for example, in the form of a generalpurpose computer that is adapted and configured to run a softwareprogram for operating the cooling system 170 of system 100 to cool slab140.

Temperature measuring device 180 is operably coupled to control system190. In operation, the amount of cooling fluid provided by way ofnozzles 200 is controlled by operating one or more valves, for example,in a valve manifold 196, if desired, in order to achieve a desiredsurface temperature of slab 140 at a given point in caster I 10.

In accordance with one embodiment of the invention, a predeterminedcooling profile is provided for the material being cast.

For purposes of illustration and not limitation, the predeterminedcooling profile can be similar to an actual cooling profile,particularly where a system made in accordance with the invention isprovided as a retrofit to an existing caster. An example of actualcooling profiles for steel are depicted in FIG. 17 at a caster speed of1.270 meters/minute with a tundish temperature of 1549 degreesCentigrade. Cooling water flow rates are provided for different coolingzones of the caster.

Specifically, the cooling curve depicted in FIG. 17 indicates the changein temperature as a function of distance traveled within the caster.Curves are depicted for actual slab surface temperature 300, actualshell thickness 400 (in millimeters) and actual slab center temperature500. An exemplary predetermined, or ideal, cooling curve 600 is alsodepicted in FIG. 17 for purposes of illustration and not limitation. Asdepicted, ideal cooling curve 600 has an appearance that is similar toactual curve 300. The shape of curve 300 depends on a variety offactors, such as the design of the caster, the material being cast, thedimensions of the slab and the casting speed, among others. The idealcooling curve 600 for steel depicted in FIG. 17 has an appearancesimilar to actual curve 300 with certain differences. For example, thehighly oscillating temperature reading of curve 300 is attributable tothe slab surface 140 coming into contact with the rollers 160 of thecaster. As depicted, ideal cooling profile 600 does not include suchvariation, but instead demonstrates a smoother appearance. However, itwill be recognized that ideal curve 600 can have a variety of shapes andstepped regions that more closely mimics the actual curve. Computermodels for cooling curves are known in the art and described, forexample, in the following publications:

“Heat Transfer and Solidification Modeling in the Continuous Casting ofMulti-Component Steels,” Hardin and Beckerman, HTD-Vol. 347, NationalHeat Transfer Conference, Volume 9, ASME 1997, pp. 9-20.

“A Transient Simulation and Dynamic Spray Cooling Control Model forContinuous Steel Casting,” Hardin, Liu, Kapoor and Beckerman,Metallurgical and Materials Transactions B, Vol. 34B, June 2003, pp.297-306.

“Development of a Model for Transient Simulation and Control of aContinuous Steel Slab Caster,” Hardin, Liu and Beckerman, MaterialsProcessing in the Computer Age III, Edited by V. R. Voller and H.Henein, The Minerals, Metals & Materials Society, 2000, pp. 61-74.

Each of the above-referenced publications is incorporated by referenceherein in its entirety. Thus, when using a system made in accordancewith the invention that is provided in the form of a retrofit kit, forexample, the system can be used to operate the caster to closely operatewithin its design range. However, a system made in accordance with theinvention can facilitate design of new, efficient casters that takemaximum advantage of the benefits accorded by the invention.

Thus, in accordance with another embodiment of the invention, an idealcooling curve can be provided that is intended for use with a newcaster, as opposed to a caster that is retrofitted with a system made inaccordance with the invention. Such an ideal cooling curve is optimizedbased on the caster design to take maximum advantage of the benefits ofactive feedback temperature control provided by the invention.

Accordingly, the temperature of the slab is preferably reduced inaccordance with a predetermined curve such as ideal cooling curve.Cooling the metal in accordance with such an ideal profile can providemany advantages. These advantages include, among other things, raisingyield due to lower defects in the material, and a higher overallconsistency of the material produced. Again, it will be understood thatthe curve will be generated empirically and used as a reference point bythe system of the invention to cool steel.

In operation, as depicted in FIG. 3, a predetermined target surfacetemperature can be input into the control system, such as from apredetermined ideal cooling curve. Next, the controller selects adesired flow rate of coolant either empirically or from other previousdata. Controller obtains the desired flow rate by operating controllablevalves in the cooling means 170. Nozzles direct coolant at slab 140,thereby cooling the slab. Temperature is continually monitored usingtemperature sensor 180. Once a steady state is achieved, any variationin the steady state, for example, a low temperature reading read bycontroller 190, can result in coolant flow being reduced until thetemperature rises to an acceptable level. Likewise, a detectedtemperature that is too high can result in a coolant increase. Inaddition

Accordingly, if desired, a real time mosaic of the surface temperatureof slab 140 can be compiled and continuously updated to continuouslyevaluate whether sufficient coolant is being supplied to slab by thecooling means 170.

In addition, by performing active feedback control as described herein,the caster can be operated at its maximum practical speed whileminimizing the chances of a breakout. For example, if the temperature isbeing monitored continuously, it is possible to detect the presence ofoverheated areas. This could be accomplished, for example through theuse of smart logic in the computer program causing an alarm when thereis a sharp temperature rise in the metal surface temperature. Reactionto a break out could be quicker due to the active link of thetemperature sensing device and the smart logic of the computer program.

Mitigating steps can also be taken, including compensating for excessivetemperature and/or temperature spikes by increasing the fluid flow inthose regions of the slab upstream of the temperature detection point.If desired, such cooling can also be applied downstream of the detectionpoint in order to properly cool the slab to the extent that the slabshould have been cooled when the temperature rise was detected.Moreover, temperature sensing devices 180 can be positionedstrategically inside caster 110 in a manner to accurately predict thecooling fluid flows in time for the cooling system to react to changingconditions of temperature. The control system 190 is adapted andconfigured to maintain the temperature across the face of the slab 140as evenly as possible near the optimum temperature.

In accordance with still another aspect of the invention, caster speedcontrol can be employed to control the surface temperature of thematerial. For purposes of illustration and not limitation, as embodiedherein, the logic of the computer program that operates control system190 may be written to include caster speed control as another method tohelp keep the metal surface temperature controlled properly. Inemploying this approach, direct temperature feedback can be utilizedfrom temperature sensors 180 to control the speed. Thus, if it isdesired to run caster 110 at a slower speed, the rate of coolant can bedecreased to match the slow down in the casting speed. This can be doneby monitoring the surface temperature and the output of the mill. If itis desired to operate caster 110 more slowly less coolant would beprovided. Conversely, if it is known that there is sufficient operatingmargin for operating safely at higher casting speeds, the rate ofcoolant flow can be selectively increased resulting in an increase ofthe casting process.

In accordance with another aspect of the invention, the control system190 can be adapted and configured to revert from a state in which itperforms active feedback control as described herein to a fail-safecondition wherein cooling is performed in accordance with apredetermined fluid control algorithm. Such predetermined algorithms arewell known in the art, and generally represent how casting machines arecurrently controlled. Providing such a fail safe mechanism can be usefulif the active feedback system malfunctions. Without a backup system inplace, it would be necessary to shut down the mill, which is costly. Byproviding a default setting, the caster can continue to operate, savinga great deal of time and money since production can continue. It mayalso be desirable to default to such a fail safe setting if it isdesired to run diagnostics on the active feedback system. When theactive feedback system is repaired and/or when such diagnostics havebeen completed, the system can be configured to resume active feedbackcontrol.

The system, method and machine readable program described herein can beprovided with a new caster delivered from a manufacturer. Alternatively,if desired, the system, method and machine readable program describedherein can be provided in the form of a retrofit kit for an existingcaster.

All statements herein reciting principles, aspects, and embodiments ofthe invention, as well as specific examples thereof, are intended toencompass both structural and functional equivalents thereof.Additionally, it is intended that such equivalents include bothcurrently known equivalents as well as equivalents developed in thefuture, i.e., any elements developed that perform the same function,regardless of structure.

Block diagrams and other representations of circuitry herein representconceptual views of illustrative circuitry and software embodying theprinciples of the invention. Thus the functions of the various elementsshown in the Figures may be provided through the use of dedicatedhardware as well as hardware capable of executing software inassociation with appropriate software, as appropriate. When provided bya processor, the functions may be provided by a single dedicatedprocessor, by a single shared processor, or by a plurality of individualprocessors, some of which may be shared. The functions of those variouselements may be implemented by, for example, digital signal processor(DSP) hardware, network processor, application specific integratedcircuit (ASIC), field programmable gate array (FPGA), read-only memory(ROM) for storing software, random access memory (RAM), and non-volatilestorage. Other hardware, conventional and/or custom, may also beincluded.

Similarly, it will be appreciated that the system flows described hereinrepresent various processes which may be substantially represented incomputer-readable medium and so executed by a computer or processor,whether or not such computer or processor is explicitly shown. Moreover,the various processes can be understood as representing not onlyprocessing and/or other functions but, alternatively, as blocks ofprogram code that carry out such processing or functions.

The methods and systems of the present invention, as described above andshown in the drawings, provide for a casting system with superiorproperties including increased yield and reliability. It will beapparent to those skilled in the art that various modifications andvariations can be made in the device and method of the present inventionwithout departing from the spirit or scope of the invention. Thus, it isintended that the present invention include modifications and variationsthat are within the scope of the appended claims and their equivalents.

1. A caster for continuously casting metal including: a) a mold adaptedand configured to mold molten metal into a metal strand; b) a coolingsystem disposed downstream of the mold adapted and configured tocontrollably cool and substantially solidify the strand before exitingthe caster; and c) a temperature measuring device adapted and configuredto detect the surface temperature of the strand, the temperature sensorincluding: i) a sensor adapted and configured to detect the temperatureof the strand; and ii) a gas purge line operably coupled to the sensor,the gas purge line being adapted and configured to deliver a gas purgeto deflect debris from a region of the strand being monitored by thetemperature sensor.
 2. The caster of claim 1, wherein the gas purgeprevents coolant from affecting accuracy of temperature measurement. 3.The caster of claim 1, wherein the sensor directly contacts the strandto measure the strand temperature.
 4. The caster of claim 3, wherein thesensor includes a thermocouple.
 5. The caster of claim 1, wherein thesensor includes a photon sensor that detects photons emitted from thestrand to measure the strand temperature.
 6. The caster of claim 5,further comprising an elongate tubular member having a first enddisposed proximate the strand and a second end disposed proximate thesensor, the tubular member being adapted and configured to permitpassage of photons emitted by the strand from the first end of thetubular member to the sensor.
 7. The caster of claim 6, wherein the gaspurge line directs the gas purge through the tubular member.
 8. Thecaster of claim 7, wherein the purge line is adapted and configured topurge debris away from a radiation path defined between the slab and thephoton sensor.
 9. The caster of claim 8, wherein the first end of thetubular member is angled to facilitate purging of debris away from theradiation path.
 10. The caster of claim 5, wherein the photon sensorincludes a pyrometer.
 11. The caster of claim 10, wherein the pyrometeris sensitive to a wavelength in at least one of (i) the ultravioletrange of the electromagnetic spectrum, (ii) the visible range of theelectromagnetic spectrum and (iii) the near infrared range of theelectromagnetic spectrum.
 12. The caster of claim 11, wherein thepyrometer is sensitive to wavelengths having a length less than about0.5 microns.
 13. The caster of claim 10, wherein the pyrometer is atwo-color pyrometer.
 14. The caster of claim 1, further comprising: a) acontrol system operably coupled to the cooling system and thetemperature sensor, the control system being adapted and configured toadjust the flow of coolant to the strand in response to a change instrand temperature detected by the temperature sensor.
 15. The caster ofclaim 14, wherein the coolant includes fluid selected from the groupconsisting of water, air and combinations thereof.
 16. The caster ofclaim 14, wherein the control system is adapted and configured toindividually control at least one of (i) an individual cooling nozzleand (ii) a bank of cooling nozzles.
 17. The caster of claim 1, whereinthe temperature sensor detects the surface temperature of the strand ata location downstream of at least one cooling nozzle.
 18. The caster ofclaim 14, wherein the control system is adapted to perform at least oneof: (i) maintaining a substantially controlled surface temperatureacross the surface of the strand while it solidifies, (ii) controllingthe speed of the caster, (iii) controlling the surface temperature ofthe stream of material by adjusting the speed of the caster or (iv)defaulting from active feedback control to a default cooling setting.